Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from matter that does not. It is defined descriptively by the capacity for homeostasis, organisation, metabolism, growth, adaptation, response to stimuli, and reproduction.

Life, particularly simple forms, spontaneously and readily arises from nonliving matter in short periods of time, today as in the past. Life is coeternal with matter and has no beginning; life arrived on Earth at the time of Earth’s origin or shortly thereafter. Life arose on the early Earth by a series of progressive chemical reactions.

Life comprises individuals, living beings, assignable to groups (taxa). Each individual is composed of one or more minimal living units, called cells, and is capable of transformation of carbon -based and other compounds (metabolism), growth, and participation in reproductive acts.

The Oparin-Haldane hypothesis suggests that life arose gradually from inorganic molecules, with “building blocks” like amino acids forming first and then combining to make complex polymers. The Miller-Urey experiment provided the first evidence that organic molecules needed for life could be formed from inorganic components.